The present invention relates to measurement of characteristics of a television system, and more particularly to a moire measurement system using spectral analysis to provide a display of moire error in a video signal.
Moire is a phenomenon that produces a spurious pattern in a reproduced television signal resulting from interference beats between two sets of periodic structures in the signal. In systems using a frequency modulated (FM) carrier, such as magnetic or video-disc record-playback systems, moire may be caused by interference between the upper sidebands of the FM carrier and the lower sidebands of harmonics of the FM carrier. As shown in FIGS. 1A and 1B if the video signal to be recorded has an input spectral component, f1, the playback signal has other spurious spectral components, such as f2. This moire signal degradation is one of the most significant in analog video tape recorders.
What is desired is a moire measurement system that gives an indication of the amount of moire error introduced into a video signal by a particular video device. The moire error may then also be compensated for to produce an error free video signal.